1. Open Unity 5.3.4 Project on 5.6.1It took a long time to import things. And after then, Everything was magenta colored. It's a common material problem. We need to 'reimport all'Material problem can be easily fixed using 'reimport all'. (sometimes, we should change some shader. Or delete old shader.)

2.No 'PlayMaker' menu.And still there's many error messages. I couldn't understand them. And there's no 'playmaker menu' on the menu bar.I'm using 'LeanTween playmaker action' from assetstore. 2 actions of them caused problem. I deleted them. This means, some old actions can cause fatal problem.

I deleted some language folders. And then, 'playmaker' menu came back.

4. But still many error messages and I couldn't run the game.I updated Playmaker. I didn't erase the asset. I just imported latest version(1.8.4).Some actions were updated. And some error messages are cleared.I pushed 'update all FSMs in build'. But problems were still remained.

5. GetComponent action's variable re-assignMy final problem was 'NavMesh Agent'. The 'get component' caused problems. At a glance, there were nothing wrong. Anyway, I re-assigned the NavMeshAgent variable's object type. And then, I could clear all the error messages.

6. Need bake light map again.This is not related with PlayMaker. Anyway after updating Unity, lightmap should be baked again.

Now...almost every problem was cleared. :-)

Updating is...really horrible. But possible!

In Short :

1. Some wrong playmaker action can cause fatal problem. We need to fix them or delete.(losing playmaker menu)2. Unity and Playmaker's version compatibility is important. Just import newer version.3. I still don't know about the language folder problem.4. 'update all FSMs in build' can clear some problems.5. Look 'GetComponent' action if you are using them. Sometimes we need to assign the variable's object type again.

Thank you for the tip. Renaming playmaker folder can save time I think.

I tried updating more than 5 times.(it took more than a day)I found solutions one by one.Old action problem, Language folder problem, updating playmaker and actions, get component action's variable problem.

Thank you for the tip. Renaming playmaker folder can save time I think.

You should not rename the playmaker folder! it will give lots of errors.By renaming the unity folder i mean where unity is installed (c:\Program Files\unity for windows i believe) so you can still use that version next to the new version.

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If unity change something, actions should be updated. And Get Component action's variable should be re-assigned.

Many things get update by unity itself, but there are things that have to be changed manually in scriptsand same thing applies to playmaker actions especially Custom Actions.

By the way, a good thing to know if you imported a newer version from Playmaker and the installer did not work for some reason, you can start it manually :go to Playmaker/Editor/Install you can click on the latest version to install it

Unless you are absolutly certain of what you do, you should never do that. Unity Project assets where not designed originally to be moved around, and so it's only a pile of hack to allow for this to happen...

instead always leave ALL packages you import as is, and simply create your own folder with your specific assets for that project, it will be a lot easier and safer down the road.